By water treatment is meant, in addition to filtration, also the measured placement of substances in the water. The placement of substances can also be combined with filtration of the water.
By filter cartridges are meant, first of all, those which have a sievelike form for mechanical filtration. Secondly, by filter cartridges is also meant those which contain, in addition to a sievelike form, at least one filter medium, e.g., in granulate form, which serves for the chemical and/or mechanical removal and/or lessening of organic and/or inorganic impurities. Such filter cartridges thus enable a nonmechanical filtration, which can be combined with a mechanical filtration. These filter cartridges are used for optimization of water, by which is meant mechanical and/or nonmechanical filtration. This includes, e.g., the softening and decalcifying of drinking water.
Filtration can be pressure operated, i.e., carried out with excess pressure or partial vacuum, or it can be gravity operated.
From U.S. Pat. No. 5,653,871 is known a filter device with filter cartridge and with a connection element. The filter cartridge has a cylindrical connection head, which is inserted from below into the seat of the connection element. In the inserted condition, the inlet opening and the supply opening on the one side are situated opposite the outlet opening and the drain opening on the other side. To fix the connection head and thus the cartridge, a kind of bayonet closure is provided in the connection element. The bayonet closure, however, has the drawback that the cartridge and/or the connection element have to be twisted as a whole when inserted, which requires a great deal of effort on the one hand, and can damage the gaskets arranged in the area of the supply and drainage opening, on the other.